diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b0005012..efe8870f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -11,6 +11,7 @@ jobs:
     strategy:
       matrix:
         php:
+          - 8.5
           - 8.4
           - 8.3
           - 8.2
diff --git a/tests/BrowserTest.php b/tests/BrowserTest.php
index fdd338d9..541129f7 100644
--- a/tests/BrowserTest.php
+++ b/tests/BrowserTest.php
@@ -22,7 +22,10 @@ public function setUpBrowser()
         $this->browser = new Browser(null, $this->loop);
 
         $ref = new \ReflectionProperty($this->browser, 'transaction');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($this->browser, $this->sender);
     }
 
@@ -31,11 +34,17 @@ public function testConstructWithoutLoopAssignsLoopAutomatically()
         $browser = new Browser();
 
         $ref = new \ReflectionProperty($browser, 'transaction');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $transaction = $ref->getValue($browser);
 
         $ref = new \ReflectionProperty($transaction, 'loop');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $loop = $ref->getValue($transaction);
 
         $this->assertInstanceOf('React\EventLoop\LoopInterface', $loop);
@@ -48,23 +57,38 @@ public function testConstructWithConnectorAssignsGivenConnector()
         $browser = new Browser($connector);
 
         $ref = new \ReflectionProperty($browser, 'transaction');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $transaction = $ref->getValue($browser);
 
         $ref = new \ReflectionProperty($transaction, 'sender');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $sender = $ref->getValue($transaction);
 
         $ref = new \ReflectionProperty($sender, 'http');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $client = $ref->getValue($sender);
 
         $ref = new \ReflectionProperty($client, 'connectionManager');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $connectionManager = $ref->getValue($client);
 
         $ref = new \ReflectionProperty($connectionManager, 'connector');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ret = $ref->getValue($connectionManager);
 
         $this->assertSame($connector, $ret);
@@ -77,23 +101,38 @@ public function testConstructWithConnectorWithLegacySignatureAssignsGivenConnect
         $browser = new Browser(null, $connector);
 
         $ref = new \ReflectionProperty($browser, 'transaction');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $transaction = $ref->getValue($browser);
 
         $ref = new \ReflectionProperty($transaction, 'sender');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $sender = $ref->getValue($transaction);
 
         $ref = new \ReflectionProperty($sender, 'http');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $client = $ref->getValue($sender);
 
         $ref = new \ReflectionProperty($client, 'connectionManager');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $connectionManager = $ref->getValue($client);
 
         $ref = new \ReflectionProperty($connectionManager, 'connector');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ret = $ref->getValue($connectionManager);
 
         $this->assertSame($connector, $ret);
@@ -104,11 +143,17 @@ public function testConstructWithLoopAssignsGivenLoop()
         $browser = new Browser(null, $this->loop);
 
         $ref = new \ReflectionProperty($browser, 'transaction');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $transaction = $ref->getValue($browser);
 
         $ref = new \ReflectionProperty($transaction, 'loop');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $loop = $ref->getValue($transaction);
 
         $this->assertSame($this->loop, $loop);
@@ -119,11 +164,17 @@ public function testConstructWithLoopWithLegacySignatureAssignsGivenLoop()
         $browser = new Browser($this->loop);
 
         $ref = new \ReflectionProperty($browser, 'transaction');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $transaction = $ref->getValue($browser);
 
         $ref = new \ReflectionProperty($transaction, 'loop');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $loop = $ref->getValue($transaction);
 
         $this->assertSame($this->loop, $loop);
diff --git a/tests/HttpServerTest.php b/tests/HttpServerTest.php
index 72d48468..7cc29a9c 100644
--- a/tests/HttpServerTest.php
+++ b/tests/HttpServerTest.php
@@ -53,15 +53,24 @@ public function testConstructWithoutLoopAssignsLoopAutomatically()
         $http = new HttpServer(function () { });
 
         $ref = new \ReflectionProperty($http, 'streamingServer');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $streamingServer = $ref->getValue($http);
 
         $ref = new \ReflectionProperty($streamingServer, 'clock');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $clock = $ref->getValue($streamingServer);
 
         $ref = new \ReflectionProperty($clock, 'loop');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $loop = $ref->getValue($clock);
 
         $this->assertInstanceOf('React\EventLoop\LoopInterface', $loop);
@@ -332,7 +341,10 @@ public function testServerConcurrency($memory_limit, $post_max_size, $expectedCo
         $http = new HttpServer(function () { });
 
         $ref = new \ReflectionMethod($http, 'getConcurrentRequestsLimit');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $value = $ref->invoke($http, $memory_limit, $post_max_size);
 
@@ -344,7 +356,10 @@ public function testServerGetPostMaxSizeReturnsSizeFromGivenIniSetting()
         $http = new HttpServer(function () { });
 
         $ref = new \ReflectionMethod($http, 'getMaxRequestSize');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $value = $ref->invoke($http, '1k');
 
@@ -356,7 +371,10 @@ public function testServerGetPostMaxSizeReturnsSizeCappedFromGivenIniSetting()
         $http = new HttpServer(function () { });
 
         $ref = new \ReflectionMethod($http, 'getMaxRequestSize');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $value = $ref->invoke($http, '1M');
 
@@ -372,7 +390,10 @@ public function testServerGetPostMaxSizeFromIniIsCapped()
         $http = new HttpServer(function () { });
 
         $ref = new \ReflectionMethod($http, 'getMaxRequestSize');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $value = $ref->invoke($http);
 
@@ -389,17 +410,26 @@ public function testConstructServerWithUnlimitedMemoryLimitDoesNotLimitConcurren
         ini_set('memory_limit', $old);
 
         $ref = new \ReflectionProperty($http, 'streamingServer');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $streamingServer = $ref->getValue($http);
 
         $ref = new \ReflectionProperty($streamingServer, 'callback');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $middlewareRunner = $ref->getValue($streamingServer);
 
         $ref = new \ReflectionProperty($middlewareRunner, 'middleware');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $middleware = $ref->getValue($middlewareRunner);
 
@@ -419,17 +449,26 @@ public function testConstructServerWithMemoryLimitDoesLimitConcurrency()
         ini_set('memory_limit', $old);
 
         $ref = new \ReflectionProperty($http, 'streamingServer');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $streamingServer = $ref->getValue($http);
 
         $ref = new \ReflectionProperty($streamingServer, 'callback');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $middlewareRunner = $ref->getValue($streamingServer);
 
         $ref = new \ReflectionProperty($middlewareRunner, 'middleware');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $middleware = $ref->getValue($middlewareRunner);
 
@@ -442,17 +481,26 @@ public function testConstructFiltersOutConfigurationMiddlewareBefore()
         $http = new HttpServer(new StreamingRequestMiddleware(), function () { });
 
         $ref = new \ReflectionProperty($http, 'streamingServer');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $streamingServer = $ref->getValue($http);
 
         $ref = new \ReflectionProperty($streamingServer, 'callback');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $middlewareRunner = $ref->getValue($streamingServer);
 
         $ref = new \ReflectionProperty($middlewareRunner, 'middleware');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $middleware = $ref->getValue($middlewareRunner);
 
diff --git a/tests/Io/ClockTest.php b/tests/Io/ClockTest.php
index 8f4b90fa..55b52426 100644
--- a/tests/Io/ClockTest.php
+++ b/tests/Io/ClockTest.php
@@ -32,7 +32,10 @@ public function testNowResetsMemoizedTimestampOnFutureTick()
         $now = $clock->now();
 
         $ref = new \ReflectionProperty($clock, 'now');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $this->assertEquals($now, $ref->getValue($clock));
 
         $this->assertNotNull($tick);
diff --git a/tests/Io/MultipartParserTest.php b/tests/Io/MultipartParserTest.php
index 7f1ec667..8754ea37 100644
--- a/tests/Io/MultipartParserTest.php
+++ b/tests/Io/MultipartParserTest.php
@@ -1048,15 +1048,25 @@ public function testWeOnlyParseTheAmountOfMultiPartChunksWeConfigured()
 
         $reflectecClass = new \ReflectionClass('\React\Http\Io\MultipartParser');
         $requestProperty = $reflectecClass->getProperty('request');
-        $requestProperty->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $requestProperty->setAccessible(true);
+        }
         $cursorProperty = $reflectecClass->getProperty('cursor');
-        $cursorProperty->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $cursorProperty->setAccessible(true);
+        }
         $multipartBodyPartCountProperty = $reflectecClass->getProperty('multipartBodyPartCount');
-        $multipartBodyPartCountProperty->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $multipartBodyPartCountProperty->setAccessible(true);
+        }
         $maxMultipartBodyPartsProperty = $reflectecClass->getProperty('maxMultipartBodyParts');
-        $maxMultipartBodyPartsProperty->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $maxMultipartBodyPartsProperty->setAccessible(true);
+        }
         $parseBodyMethod = $reflectecClass->getMethod('parseBody');
-        $parseBodyMethod->setAccessible(true);
+        if (PHP_VERSION_ID < 80100) {
+            $parseBodyMethod->setAccessible(true);
+        }
 
         $this->assertSame(0, $cursorProperty->getValue($parser));
 
diff --git a/tests/Io/RequestHeaderParserTest.php b/tests/Io/RequestHeaderParserTest.php
index 87d6bf1b..c444f64d 100644
--- a/tests/Io/RequestHeaderParserTest.php
+++ b/tests/Io/RequestHeaderParserTest.php
@@ -856,7 +856,10 @@ public function testServerParamsWillBeRememberedUntilConnectionIsClosed()
         $connection->emit('data', array("GET /foo HTTP/1.0\r\nHost: example.com\r\n\r\n"));
 
         $ref = new \ReflectionProperty($parser, 'connectionParams');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $this->assertCount(1, $ref->getValue($parser));
 
diff --git a/tests/Io/StreamingServerTest.php b/tests/Io/StreamingServerTest.php
index b1410fad..d62da6aa 100644
--- a/tests/Io/StreamingServerTest.php
+++ b/tests/Io/StreamingServerTest.php
@@ -2312,11 +2312,17 @@ public function testResponseWithoutExplicitDateHeaderWillAddCurrentDateFromClock
         });
 
         $ref = new \ReflectionProperty($server, 'clock');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $clock = $ref->getValue($server);
 
         $ref = new \ReflectionProperty($clock, 'now');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($clock, 1652972091.3958);
 
         $buffer = '';
@@ -3156,7 +3162,10 @@ public function testNewConnectionWillInvokeParserOnce()
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3173,7 +3182,10 @@ public function testNewConnectionWillInvokeParserOnceAndInvokeRequestHandlerWhen
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3196,7 +3208,10 @@ public function testNewConnectionWillInvokeParserOnceAndInvokeRequestHandlerWhen
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3221,7 +3236,10 @@ public function testNewConnectionWillInvokeParserOnceAndInvokeRequestHandlerWhen
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3246,7 +3264,10 @@ public function testNewConnectionWillInvokeParserTwiceAfterInvokingRequestHandle
         $parser->expects($this->exactly(2))->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3271,7 +3292,10 @@ public function testNewConnectionWillInvokeParserTwiceAfterInvokingRequestHandle
         $parser->expects($this->exactly(2))->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3297,7 +3321,10 @@ public function testNewConnectionWillInvokeParserOnceAfterInvokingRequestHandler
         $parser->expects($this->once())->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
@@ -3323,7 +3350,10 @@ public function testNewConnectionWillInvokeParserTwiceAfterInvokingRequestHandle
         $parser->expects($this->exactly(2))->method('handle');
 
         $ref = new \ReflectionProperty($server, 'parser');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
         $ref->setValue($server, $parser);
 
         $server->listen($this->socket);
diff --git a/tests/Io/TransactionTest.php b/tests/Io/TransactionTest.php
index 284d059f..f1a386eb 100644
--- a/tests/Io/TransactionTest.php
+++ b/tests/Io/TransactionTest.php
@@ -30,7 +30,10 @@ public function testWithOptionsReturnsNewInstanceWithChangedOption()
         $this->assertNotSame($transaction, $new);
 
         $ref = new \ReflectionProperty($new, 'followRedirects');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $this->assertFalse($ref->getValue($new));
     }
@@ -44,7 +47,10 @@ public function testWithOptionsDoesNotChangeOriginalInstance()
         $transaction->withOptions(array('followRedirects' => false));
 
         $ref = new \ReflectionProperty($transaction, 'followRedirects');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $this->assertTrue($ref->getValue($transaction));
     }
@@ -59,7 +65,10 @@ public function testWithOptionsNullValueReturnsNewInstanceWithDefaultOption()
         $transaction = $transaction->withOptions(array('followRedirects' => null));
 
         $ref = new \ReflectionProperty($transaction, 'followRedirects');
-        $ref->setAccessible(true);
+
+        if (PHP_VERSION_ID < 80100) {
+            $ref->setAccessible(true);
+        }
 
         $this->assertTrue($ref->getValue($transaction));
     }